Title

Author

Date of Graduation

Document Type

Degree Name

Master of Science in Biology

College/School

College of Arts and Sciences

Department/Program

Biology

First Advisor

Christina Tzagarakis-Foster

Second Advisor

James Sikes

Third Advisor

Juliet Spencer

Abstract

DAX-1 (NR0B1) is an orphan nuclear receptor that plays a key role in the development and maintenance of steroidogenic tissue in mammals. Dax-1 is also expressed in mouse embryonic stem (ES) cells and is required to maintain pluripotency. Duplication of the X-chromosome in the region containing the NR0B1 gene results in sex reversal, and mutations in NR0B1 cause adrenal hypoplasia congenita. DAX-1 has been observed to act as a corepressor of other nuclear receptors including androgen receptor (AR), estrogen receptor (ER), and steroidogenic factor 1 (SF-1). In addition to pluripotent ES cells, DAX-1 is primarily expressed in select tissues of the body such as testes, ovaries, adrenal cortex and breast. In some cases, changes in DAX-1 expression may serve as an indicator of aberrant growth. For example, DAX-1 expression is greatly reduced in ER+ breast cancer patient samples and several ER+ cell lines; however the mechanism leading to this change in DAX-1 expression is unknown. Here, we propose that expression of DAX-1 may be governed by epigenetic mechanisms.

We sought to determine whether promoter region CpG island methylation and expression of DAX-1 were inversely related , and if the loss of DAX-1 expression in the breast cancer cell line MCF-7 is due to epigenetic mechanisms. Using gene expression assays and bisulfite sequencing, we have confirmed the relationship between methylation status and DAX-1 expression in MCF7 and A549 cancer cell lines. We have further analyzed the DAX-1 CpG island to observe the presence of epigenetic readers MeCP2 and MBD1 that link methylation to gene repression, suggesting DAX-1 is expressed and regulated differentially by epigenetic mechanisms in the cancer cell lines MCF7 and A549.